Environmentally friendly growth of well-developed LiCoO₂ crystals for lithium-ion rechargeable batteries using a NaCl flux

High quality LiCoO₂ crystals, useful as cathode material for lithium-ion rechargeable batteries, were successfully grown at a holding temperature of 800-1000 °C using the NaCl flux cooling method. The morphology, structure, size uniformity, and crystallinity of the obtained LiCoO₂ crystals were obviously dependent on the growth conditions, such as the holding temperature and the starting composition. Well-developed, highly crystalline LiCoO₂ crystals were first grown at a holding temperature of 900 °C from a NaCl flux. The grown LiCoO₂ crystals had a hexagonal barrel-shaped structure with well-developed {001}, {104}, {101}, and {102} faces. On the basis of the powder X-ray diffraction data, the lattice parameters of the crystals were determined as a = 2.816 and c = 14.077 Å. These values agree approximately with those from the literature (a = 2.816 and c = 14.052 Å). The average crystal size was about 1.4 μm, which is a relatively small size when compared to previous reports. Transmission electron microscopy images indicate that the LiCoO₂ crystals were of very good crystallinity. It was confirmed that the charge and discharge capacities of the lithium-ion rechargeable batteries containing the grown LiCoO₂ crystals were 138 and 130 mAh•g^-1, respectively, values that correspond to the available capacity of 137.5 mAh•g^-1. The discharge capacity of the grown LiCoO₂ crystal is greater at 10 C than that of commercially available crystals.